Aircraft include many parts that are suitable for monitoring and periodic replacement. For example, many aircraft braking systems include one or more servo valves suited for converting variations in an electrical signal into variations in how much hydraulic fluid is transmitted to a brake actuator. Such servo valves can be used to control powerful hydraulic cylinders with small electrical signals. They can provide precise levels of control over force, position, pressure, and velocity, etc., such as by electrically coupling to a power source to apply a desired amount of electrical current to the servo valve in order to actuate a poppet internal to the servo valve and suitably open or close the servo valve to thus control the amount of hydraulic pressure output by the servo valve. Sensors in communication with servo valves can monitor the amount of electrical current (electrical signal) input into the servo valve and the corresponding hydraulic pressure output from the servo valve (hydraulic pressure signal).
In many closed loop systems, such as aircraft braking systems, it can be imperative to maintain a desired hydraulic pressure output from a servo valve, regardless of the input electrical signal, in order to maintain proper braking forces on an actuator in order to impact the wheel of an aircraft. Accordingly, it can be difficult to ascertain a deteriorating condition or fault in a servo valve if the hydraulic pressure signal output from the servo valve is maintained at a nearly constant level by compensating (e.g., increasing or decreasing) the electrical signal input into the servo valve.